Photosensitive composition



' 2,874,047 PHOTOSENSITIVE COMPOSITION Peter A. van der Meulen, HighlandPark, N. J., and Paul-B. Gilman, Jr., Rochester, N. Y., assignors to theUnited States of America as represented by the Secretary of the AirForce Application November 4, 1957 Serial No. 694,462

9 Claims. (Cl. 96-94) No Drawing.

The present invention relates generally to photosensitive materials and,as illustrated herein, relates more particularly to such materialswherein the heat developed image may be removed and the originalphotosensitivity of the material will be restored.

Photothermographic material may be differentially modified or decomposedby the action of heat in accordance with previous response to light toproduce a visible image. Silver oxalate and mercurous oxalate have beenused for the manufacture of photographic layers. These materials,however, have not been entirely satisfactory since they have arelatively low sensitivity to light and hence require relatively longexposures to produce a negative which when developed will havesufiicient contrast. Somewhat higher photothermal sensitivity isproduced by a coprecipitated mixture of silver and mercurous oxalate.Sensitivity may be still further increased by adding an excess ofpotassium oxalate. However, such compositions can be used only oncesince it is not possible to restore light sensitivity to the originallayer.

One object of the present invention is to-provide a material which ishighly sensitive to light and which may be reactivated by a simpleprocess for reuse. To this end, a mercurous iodide-silver iodide mixtureis provided which is dispersed in a gelatin solution and coated on asuitable surface. Preferably, and as illustrated, the mixture containsmercurous iodide (Hg l and silver iodide (AgI) wherein the silver iodidecomprises from .1 to 90 mole percent of the mixture, since such a ratioprovides greater sensitivity over a wider wavelength range.

The present invention will become more apparent from the followingdescription of a method for preparing a mixture of iodides by the use ofwhich highly sensitive photosensitive material is produced. The methodof preparing the iodides and the range of mole ratios in which they areto be combined may be varied within wide limits. The reactiontemperatures and the reaction time may also be varied within reasonablelimits without involving any substantial change in the photosensitivityof the mixture.

The present invention is based broadly on the discovery that mercurousiodide-silver iodide mixtures containing from .1 to 90 mole percent ofsilver iodide are photosensitive and latent images may be developedeither chemically or thermally, after relatively short exposures tolight. Generally, the photosensitivity of the mixture varies as the molepercent of silver iodide in the mixture varies.

The present mixture of ingredients may be developed thermally by heatingthe exposed mixture for four minutes at a temperature of approximately105 C.

The image developed thermally is stable but it is possible to restorethe mixture to its initial photosensitive condition by continued heatingat 130 C. for thirty minutes and the mixture therefore is reusable.However, thermal reversal is not possible when the mercurousiodide-silver iodide mixture is chemically developed.

, 2,874,047 Patented Feb. 17, 1959 An example for preparing aphotographic emulsion of mercurous iodide and silver iodide is asfollows:

A. Potassium iodide g 6.0 Distilled water ml 300 Mercurous nitrate g11.2

p 6 N nitric acid ml .10 Distilled water ml 400 C. Silver nitrate g .46Distilled water ml D. Potassium iodide g .40

. Distilled water ml- 100 E. Gelatin g 37.5

Distilled water ml 150 The various materials are dissolved in distilledwater in the amounts noted above. The procedures outlined below arecarried under darkroomconditions using a red safelight.

Solution A is added very slowly and with rapid agitation to Solution B.The resulting precipitate is stirred for two minutes and then Washed bydecantation with approximately three liters of distilled water.

Solution C is added within thirty seconds to rapidly agitated solutionD. The resulting silver iodide precipitate is stirred for two minutesand then is added directly to the mercurous iodide-water mixtureresulting from the reactions between solutions A and B. The mixedprecipitates are stirred for three minutes, washed by decantation anddispersed in solution E at 50 C.

The emulsion is then passed through a hand homogenizer and coated ontransparent slides formed of suitable clear plastic or glass. The slidesare dried overnight and are then ready for use.

It is to be noted that the mercurous-iodide and silver iodide mixturesmay vary from .'1 to 90 mole percent of silver iodide. The best results,however, are obtained when the silver iodide is present in the mixturein 1.0 to '10 mole percent. The above mixtures are highly sensitive tolight in the visible range up to approximately 490 millimicrons.

After the coated slide has been exposed, the latent image thereon may bethermally developed by placing the properly exposed plate on a heatedblock emulsion side up at a temperature of C. for a period of fourminutes.

Chemical development can be carried out in the conventional manner byimmersing the exposed plate for two minutes in 1:2 solution of KodakDektol.

It is apparent that the present invention may be used for makingreversible print-out materials for the production of photographs ofdocuments, for the rapid production of reversible negatives or positivesby thermal development and for the production of irreversible negativesor positives with'chemical development.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent of the United States is:

l. A photographic element comprising a support, a gelatine carrier, andheat sensitive material carried thereby, said heat sensitive materialcomprising from 0.1 to 90 mole percent of silver iodide and from 99.9 to10 mole percent of mercurous iodide.

2. A photographic element comprising a support, a gelatine carrier, andheat sensitive material carried thereby, said heat sensitive materialcomprising from 1.0 to 10 mole percent of silver iodide and from 99 to90 mole percent of mercurous iodide.

3. A photographic element comprising a support and a heat sensitivegelatine layer thereon containing gelatin and light and heat sensitivematerials, said materials com- 99.9 to mole percent of mercurous iodide.

4. A photographic element comprising a support and heat sensitivegelatine layer-thereon comprising gelatin and light and heat sensitivematerials, said materials comprising 0.1 to 90 mole percent of silveriodide and 99.9 to 10 mole percent of mercurous iodide.

5. A method of making a visible image which comprises sensitizing agelatine layer with light sensitive mixture of .1 to 90 mole percentsilver iodide and 10 to 99.9 mole percent of mercurous iodide andheating said layer to a temperature of about 105 C. to produce an imagetherein.

6. A method of making a visible image which comprises sensitizing agelatine layer with light sensitive mixture of .1 to 90 mole percent ofsilver iodide and 10 to 99.9 mole percent of mercurous iodide, exposingsaid layer to light, and then submitting said'layer to a tem perature ofabout 105 C. to develop the latent image therein, and finally submittingsaid layer to a temperature of about 130 C. to restore the sensitivityof said layer.

7. A method of making a visible image which commately 105 C. for aperiod of approximately four minutes tosensitize said layer.

8. A method of making a visible image which comprises sensitizing agelatine'layer with a light and heat sensitive mixture of .1 to molepercent of silver iodide and 10 to 99.9 mole percent of mercurousiodide, submitting said layer to heat at a temperature of approximatelyC. for a period of approximately four minutes to sensitize said layer,and finally heating said layer to a temperature of about C. for a longerperiod of time to restore the sensitivity of said layer.

9. A method of making a visible image which comprises sensitizing agelatine layer with a light and heat sensitive mixture of .1 to 90 molepercent of silver iodide and 10 to 99.9 mole percent of mercurousiodide, submitting said layer to heat at a temperature of approximately105 C. for a period of approximately four minutes to sensitize saidlayer, and finally heating said layer to a temperature of approximately130 C. for a period 20 of approximately thirty minutes.

prises sensitizing a gelatine layer with alight and heat sensitivemixture of .1 to 90 mole percent of silver iodide and 10 to 99.9 molepercent mercurous iodide, and submitting said layer to heat at atemperature of approxi- References Cited in the file of this patentUNITED STATES PATENTS 1,758,530 Frankenburger et al Dec. 10, 1929 252,700,610 Suchow et a1. Jan. 25, 1955 Carroll et a1. Dec. 27, 1955

1. A PHOTOGRAPHIC ELEMENT COMPRISING A SUPPORT, A GELATINE CARRIER, ANDHEAT SENISTIVE MATERIAL CARRIED THEREBY, SAID HEAT SENSITIVE MATERIALCARRIED TO 90 MOLE PERCENT OF SILVER IODINE AND FROM 0.1 MOLE PERCENT OFMERCUROUS IODIDE.